According to the prior art of a single direction ratchet wrench disclosed in U.S. Pat. No. 5,979,274, it comprises a main body whose two ends are one handle and one function end respectively. The function end has a first housing with a ratchet wheel allocated inside, a second housing caved in the inner wall of the first housing, a pawl confined in the second housing, and an elastic element lodged in a recess. When the elastic element pushes the pawl, the retaining cogs of the pawl and the ratchet teeth of the ratchet wheel are engaged together. Nevertheless, the recess to lodge the elastic element is drilled in the curved wall of the second housing. During manufacturing, the drill bit has to reach in the second housing with a bevel angle, in order to avoid contacting with the wall of the first housing, and drills a slanted recess from the curved wall of the second housing. Not only is the process difficult, but the elastic element lodged in the recess tends to be slantwise and poorly functioned.
Another prior art of a single direction ratchet wrench disclosed in U.S. Pat. No. 7,444,903 B1, it comprises a main body, a pawl, a ratchet wheel, a spring, a C-shape clip and a position ring. The main body has a first housing at its one end and a curved second housing in the wall of the first housing. An annular trough is at the top portion of the first housing and an annular flange at the bottom. The pawl is arc shaped. Its front side is a concave surface which has retaining cogs and a sliding surface successively arranged on it, and its rear side, opposite to the retaining cogs, has a limit surface and, opposite to the sliding surface, links with a spring. Both the top and the bottom portions of the ratchet wheel have an annular groove, and the two annular grooves allow the annular flange and the position ring to lodge in respectively. A C-shape clip clamps the ring and the groove tightly so that the ratchet wheel is positioned within the first housing by the concealed ring. This prior art does not require drilling a recess in the second housing to lodge the spring, but it still has following disadvantages:
1. It comprises six components: a main body, a pawl, a ratchet wheel, a spring, a C-shape clip and a position ring. The more the components are, and the higher the assembly cost is.
2. It still requires drilling a hole on the rear side of the pawl for the spring to be lodged. Because the rear side of the pawl is a curve, it makes the drilling much more difficult, especially at the summit of the curve. When the drill bit is spinning at a high speed and contacting with the surface of the curve, it is easily displaced along the curve. Therefore, it makes the drilling inaccurate as well and possibly damages the hole and the bit.
3. The recess to lodge the spring is located on the rear side, close to the middle portion, of the pawl in order for the pawl to be completely pushed and engaged with the ratchet wheel, but the spring does not have enough elasticity to disengage the pawl. In this case, it will cause the pawl to still engage with the ratchet wheel when the wrench is revolved in opposite direction and the wrench is unable to be revolved counterclockwise against the ratchet wheel.
4. The depth of the recess is limited, and so is the length of the spring. Therefore, the spring can only supply insufficient elasticity and cause the interaction between the pawl and the ratchet wheel uneven.